JP2006001783A - Mono-dispersed dry silica particle powder and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica particle powder which is highly mono-dispersed and comprises flaky silica primary particles and/or leafy silica secondary particles, by drying slurry of leafy silica secondary particles through a simple method while maintaining their state in the aqueous slurry. <P>SOLUTION: The highly mono-dispersed dry silica particle powder is provided by (i) hydrothermally treating silica hydrogel etc., in the presence of an alkali metal salt to form flaky silica tertiary coagulated particles, (ii) disintegrating and dispersing the silica tertiary coagulated particles in an aqueous slurry state to form the aqueous slurry comprising flaky silica primary particles and/or leafy silica secondary particles, (iii) adding an aqueous emulsion of a silicon-based compound to the aqueous slurry, mixing it and treating the mixture in a slurry state, (iv) drying it and (v) subjecting it to dry-disintegration. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a dry silica particle powder in which the silica flake primary particles and / or the leaf-like silica secondary particles formed by superimposing a plurality of these are usually monodisperse, which are difficult to obtain from an aqueous slurry, and The present invention relates to a method for directly producing the dry silica particle powder from the aqueous slurry.

  The inventors of the present invention have previously described a novel aqueous slurry of self-film-formable foliar silica secondary particles formed by laminating a plurality of flake primary particles of scaly silica parallel to each other in parallel. (For example, refer to Patent Document 1).

  The aqueous slurry of the leaf-like silica secondary particles having the particle form of the laminated structure is the aqueous slurry composed of an organic polymer material such as an acrylic resin type, an epoxy resin type, a urethane resin type, or a fluorine resin type as the slurry. When blended in a paint, due to the unique particle morphology and physical properties of the secondary particles, it is possible to impart excellent properties such as water resistance, acid resistance, alkali resistance, and weather resistance to the formed coating film. it can.

  That is, basically, since the leaf-like silica secondary particles themselves are excellent in self-forming properties, they are oriented in the coating film and exist in a state of being stacked on each other. Gives strong adhesion. For example, when the pencil hardness of a coating film of a normal water-based organic paint is about B to 4B, when the silica secondary particles are blended, for example, the hardness is improved to about H to 4H.

  The leaf-like silica secondary particles created by the present inventors are blended in various coating forming compositions such as coating agents, floor polish compositions and adhesives in addition to paints, and the film quality and the like are remarkably increased. It is also extremely useful as an improved filler. However, since the leaf-like silica secondary particles are basically obtained by crushing an aqueous slurry of silica tertiary aggregate particles under specific conditions using a medium bead mill or the like. Naturally, the form is limited to the state of the aqueous slurry.

  Therefore, the leaf-like silica secondary particles in an aqueous slurry state cannot be directly blended into an organic solvent type (non-aqueous) coating composition, coating agent, ink composition or wax composition, and contain an organic solvent. It is also difficult to blend into resin compounds and cosmetics.

  Naturally, the most preferable form of the leaf-like secondary particles when used as a filler is, of course, the dry powder, so that the present inventors have obtained an aqueous slurry of the leaf-like silica secondary particles. A method for obtaining a dry powder of silica secondary particles by drying the powder was also studied earnestly. However, the leaf-like silica secondary particles are due to their strong self-film-forming properties or exhibit extreme cohesiveness during drying, and it is expected that the aqueous slurry is dried into a dry powder. I found it more difficult.

  That is, when the above-described slurry is directly dried by a dryer, the particles are easily aggregated and fixed in the drying process. The dried particles that have become agglomerated by sticking are no longer easily pulverized, and when pulverized, the shape of the leaf-like secondary particles of each particle is destroyed. In addition, it was found that if the aqueous slurry was spray-dried, a dry powder of leaf-like silica secondary particles was obtained, but this is a solid content concentration in the slurry before drying of 1% by mass or less, This is limited to an extremely dilute slurry that is not economically viable at all, and is not a practical and economical method.

  Furthermore, the present inventors added an organic solvent to the aqueous slurry of the leaf-like secondary particles, and azeotropically distilled to replace the water with the organic solvent, thereby obtaining an organic solvent-based slurry of the particles. It has also been proposed that if the solvent is evaporated and dried and dried, the particles can be made into a dry particle powder without aggregation and solidification during the drying (see Patent Document 2).

  However, in order to obtain a dry powder, once the water-based slurry is purposely converted into an organic solvent-based slurry and further the operation for removing the organic solvent is added, an extra step is added in the process. In addition to being wasteful, it is extremely cumbersome.In addition, the use of organic solvents is more difficult in handling organic solvents, which are hazardous materials, in work environments, and in the case of handling only water, such as condensation and recovery. In terms of facilities, the load is extremely large, and it is practically difficult to say that the method can be implemented economically.

JP 2001-163613 (Claims (Claims 1 to 3, Claims 26 to 31), [0069] to [0071]) JP 2003-267721 (Claims (Claims 5 to 8))

  The object of the present invention is to dry the slurry of the above-mentioned leaf-like silica secondary particles while maintaining the state in the water slurry by a simple method, and from the silica flake primary particles and / or the leaf-like silica secondary particles. And providing a highly monodispersed dry silica particle powder.

  According to the present invention, the following highly dispersed dry silica particle powder and a method for producing the same are provided.

[1]
Highly monodispersed dry silica particles characterized in that they are composed of silica flake primary particles and / or leaf-like silica secondary particles formed by overlapping a plurality of the primary particles in parallel with each other. Powder.

[2]
The dry silica particle powder according to [1], whose surface is treated with a silicon compound.

[3]
The dry silica particle powder according to [1] or [2], wherein the silica flake primary particles and / or the leaf-like silica secondary particles are layered polysilicic acid.

[4]
Any of [1] to [3], wherein the main peak in the X-ray diffraction analysis of the silica flake primary particles and / or the leaf-like silica secondary particles is silica corresponding to silica-X and / or silica-Y. The dried silica particle powder according to claim 1.

[5]
A method for producing a dry silica particle powder in which silica flake primary particles and / or leaf-like silica secondary particles are highly monodispersed, wherein (i) silica hydrogel, activated silicic acid or hydrous silicic acid is alkalinized Hydrothermal treatment is performed in the presence of a metal salt, and the flaky primary particles of scaly silica are oriented in parallel with each other in parallel with each other, and the flaky silica secondary particles are three-dimensional. (Ii) pulverizing and dispersing the silica tertiary aggregate particles in an aqueous slurry state, and A step of forming an aqueous slurry comprising silica flake primary particles and / or leaf-like silica secondary particles; (iii) an aqueous slurry comprising said silica flake primary particles and / or leaf-like silica secondary particles; A process comprising adding and mixing a compound water-based emulsion to treat in a slurry state, (iv) a drying process for drying the mixture, and (v) dry crushing the dry powder. A method for producing monodispersed dry silica particle powder.

[6]
[2] The method for producing a dry silica particle powder according to [5], wherein the silicon-based compound aqueous emulsion is added to and mixed with at least 2% by mass of the silicon-based compound aqueous emulsion on a solid basis.

[7]
The method for producing a dry silica particle powder according to [5] or [6], wherein the silica flake primary particles and / or the leaf-like silica secondary particles are layered polysilicic acid.

[8]
Any of [5] to [7], wherein the main peak in the X-ray diffraction analysis of the flake primary particles and / or the leaf-like silica secondary particles is silica corresponding to silica-X and / or silica-Y. A method for producing the dry silica particle powder according to claim 1.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flow sheet for explaining a method for producing monodispersed dry silica particle powder of the present invention, which is roughly a leaf-like shape obtained by crushing / dispersing the silica tertiary aggregate particle aqueous slurry 30. An aqueous slurry 50 of silica secondary particles is added and mixed with a silicon-based compound aqueous emulsion 60, and the leaf-like silica powder aggregate 100 obtained by carrying out the treatment step 70 and the drying step 80 in a slurry state is dissolved in a dry manner. The dried silica particle powder 120 is crushed 110.

(Silica tertiary aggregate particle production step)
In the method for producing an organic medium slurry of silica particles of the present invention, first, a step of forming an aqueous slurry 30 of silica tertiary aggregate particles is performed.

  That is, in this process, an alkali metal salt is heated in a pressurized pressure vessel such as an autoclave using any one of silica hydrogel, activated silicic acid, or hydrous silicic acid (hereinafter referred to as “silica hydrogel etc.” 10) as a starting material. A hydrothermal treatment step 20 is performed in the presence of water, and an aqueous slurry 30 of scaly silica tertiary aggregate particles composed of tertiary particles having gaps formed by three-dimensional irregularly overlapping leaf-like silica particles is obtained. To form.

  Here, the silica hydrogel can produce silica-X, silica-Y, etc., which are silica tertiary aggregate particles, at a low temperature and in a short time, with a high yield without generating crystals such as quartz. Since it is possible to do so, it is the most preferable, and the case where silica hydrogel is used as a starting material will be described below as an example.

  The silica hydrogel is a particulate silica hydrogel, and the particle shape thereof may be true spherical (spherical) or amorphous, and the granulating method can be appropriately selected. A spherical silica hydrogel is produced by mixing an alkali silicate aqueous solution and a mineral acid aqueous solution to form a silica sol in a short time, and at the same time, releasing it into a gaseous medium and gelling it in the gas.

Specifically, an alkali silicate aqueous solution and a mineral acid aqueous solution are introduced into a container provided with a discharge port from a separate introduction port and instantaneously uniformly mixed, and the SiO ₂ concentration is 130 g / L or more, pH 7 A silica sol of ˜9 is generated, and the sol is discharged from the outlet and gelled in the air. This is dropped in an aging tank filled with water and aged for several minutes to several tens of minutes, and an acid is added and washed with water to obtain a spherical silica hydrogel.

  Using such a silica hydrogel as a starting material, it is heated in a heating pressure vessel such as an autoclave and subjected to hydrothermal treatment to produce a silica tertiary aggregate particle aqueous slurry 30. In addition, although spherical silica hydrogel may be used as it is, it is preferably pulverized or coarsely pulverized to a particle size of about 0.1 to 6 mm.

The total silica concentration in the treatment liquid in the autoclave (a value obtained by adding silica brought into the system by sodium silicate as an alkali metal salt) is 1 to 30% by mass, preferably 10 as SiO _{2 on the} basis of all charged raw materials. ˜20 mass%. In the hydrothermal treatment, it is preferable that an alkali metal salt (alkali hydroxide, alkali silicate, alkali carbonate, or the like) coexists in the silica hydrogel.

The pH of the system is preferably pH 7 or more, more preferably pH 8 to 13, more preferably pH 9 to 12.5, and the amount of alkali is expressed in silica / alkali molar ratio (SiO ₂ / Na ₂ O etc.). If it does, it will be 4-15 mol / mol, Preferably, it is the range of 7-13 mol / mol.

  The hydrothermal treatment is performed at a temperature range of 150 to 220 ° C., preferably 160 to 200 ° C. for 3 to 50 hours, preferably about 5 to 40 hours. Further, silica-X, silica-Y, or the like may be used as a seed crystal.

  In addition to the method using silica hydrogel as a starting material as described above, the silica tertiary aggregate particles of the present invention can be obtained in the same manner by using activated silicic acid or hydrous silicic acid (so-called white carbon). The aqueous slurry 30 can be synthesized.

(Crushing / dispersing step in silica tertiary aggregate particle slurry)
In the present invention, silica tertiary aggregate particles thus obtained in the form of an aqueous slurry (this is because the leaf-like secondary particles generated by the hydrothermal reaction are further irregularly overlapped three-dimensionally, The silica agglomerate particles are formed.) 30 is crushed and dispersed in a slurry state to obtain an aqueous slurry 50 of leaf-like silica secondary particles.

For the crushing in the slurry state, the silica tertiary aggregate particle slurry is washed with water and solid-liquid separated using a solid-liquid separation / water washing device such as a belt filter, and further repulped with water as necessary to obtain SiO ₂ concentration. 1-30 mass% water slurry is supplied, and the slurry 30 is supplied to a wet pulverizer (crusher) such as a wet bead mill, a wet ball mill, or a thin film swirl type high-speed mixer, and the silica tertiary aggregate particles in the slurry Is crushed and dispersed 40 to obtain an aqueous slurry 50 of leaf-like silica secondary particles.

  By this crushing treatment, most of the scaly silica tertiary aggregate particles become leaf-like silica secondary particles, but the secondary particles (that is, the silica flake primary particles have an inter-surface spacing). Part of the particles that are oriented in parallel and overlapped to form secondary particles are further separated and crushed into silica flake primary particles that are the structural unit. Therefore, the leaf-like silica secondary particles mentioned here may be a part of them or a mixture of a considerable amount of flake primary particles, and precisely, “the flake silica primary particles and / or the leaf-like silica 2”. This state is simply referred to as “leafy silica secondary particles” or simply “leafy silica secondary particles” for convenience of explanation.

  As the apparatus used for wet crushing, as described above, wet crushing apparatuses such as a wet bead mill and a wet ball mill that are mechanically stirred at high speed using a grinding medium are preferable. The aggregated particles are crushed into leaf-like silica secondary particles, and the produced leaf-like silica secondary particles (and flake primary particles) are crushed and broken down without pulverizing and destroying the basic laminated structure as much as possible. A wet bead mill using media beads such as alumina or zirconia having a diameter of 0.2 to 1.0 mm for dispersion is particularly desirable.

(Treatment of silica secondary particle aqueous slurry with silicon compound aqueous emulsion)
In the present invention, the process 70 is performed in which the silicon-based compound 60 in an aqueous emulsion state is added to and mixed with the leaf-like silica secondary particle aqueous slurry 50 prepared as described above and processed in a slurry state.

(Silicon compounds)
The silicon compound used here is agglomeration / adherence in the drying process of the silica particles from the aqueous slurry by surface treatment such as contact, adhesion, adsorption or coating of the surface of the secondary silica particles. Although it will not specifically limit if an effect | action can be prevented or relieve | moderated, For example, what is called a silicone oil represented by Formula (1) is preferable. Hereinafter, a case where silicone oil is used as the silicon compound will be described as an example.

(Here, R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen, an alkyl group having 1 to 30 carbon atoms, an epoxy group, an amino group, a carboxyl group, an alkoxyl group, a phenyl group, a polyoxy group) (It is selected from an alkylene group, a mercapto group, and an aryl group, and m represents an integer of 1 or more, and n represents 0 or an integer of 1 or more.)

As an example of the silicone oil represented by the formula (1), those in which R ¹ , R ² , R ³ , R ⁴ are hydrogen, an alkyl group, or a phenyl group (so-called straight silicone oil) include methyl hydro Gen silicone oil (R ¹ = H, R ² , R ³ , R ⁴ = CH ₃ ), dimethyl silicone oil (R ¹ , R ² , R ³ , R ⁴ = CH ₃ ), diethyl silicone oil (R ¹ , R _{^{2 = C 2 H 5, R}} 3, R 4 = CH 3), diisopropyl silicone oil ^{(R 1, R 2 = C} 3 H 7, R 3, R 4 = CH 3), dibutyl silicone oil (R ^1, R ² = C ₄ H ₉ , R ³ , R ⁴ = CH ₃ ), diamyl silicone oil (R ¹ , R ² = C ₅ H ₁₁ , R ³ , R ⁴ = CH ₃ ), dihexyl silicone oil (R ¹ , R ² = C ₆ H ₁₃ , R ³ , R ⁴ = CH ₃ ), Zira Uril silicone oil ^{(R 1, R 2 = C} 11 H 23, R 3, R 4 = CH 3), distearyl silicone oil ^{(R 1, R 2 = C} 17 H 35, R 3, R 4 = CH 3) Methyl phenyl silicone oil (R ¹ = φ (φ represents a phenyl group; the same applies hereinafter) R ² , R ³ , R ⁴ = CH ₃ ), diphenyl silicone oil (R ¹ , R ² = φ, R ³ , R ⁴ = CH ₃ ), ethyl phenyl silicone oil (R ¹ = φ, R ² = C ₂ H ₅ , R ³ , R ⁴ = CH ₃ ), isopropyl phenyl silicone oil (R ¹ = φ, R ² = C ₃₎ H ₇ , R ³ , R ⁴ = CH ₃ ), butylphenyl silicone oil (R ¹ = φ, R ² = C ₄ H ₉ , R ³ , R ⁴ = CH ₃ ), amylphenyl silicone oil (R ¹ = φ R ² = C ₅ H ₁₁ , R ³ , R ⁴ = CH ₃ ), hexylphenyl silicone oy (R ¹ = φ, R ² = C ₆ H ₁₃ , R ³ , R ⁴ = CH ₃ ), lauryl phenyl silicone oil (R ¹ = φ, R ² = C ₁₁ H ₂₃ , R ³ , R ⁴ = CH ₃ ), stearyl phenyl silicone oil (R ¹ = φ, R ² = C ₁₇ H ₃₅ , R ³ , R ⁴ = CH ₃ ) and the like.

In addition, as so-called modified (reactive) silicone oil, at least one of R ¹ , R ² , R ³ , and R ⁴ is an epoxy group such as glycidyl group, glycidoxyethyl glycidoxypropyl; amino group, methyl Amino group such as amino group, dimethylamino group, isopropylamino group, anilino group, toluidino group, xylidino group; carboxyl such as carboxyl group, methoxycarbonyl group, ethoxycarbonyl group, isopropoxycarbonyl group, acetoxy group, benzoxyloxy group Group: alkoxyl group such as methoxy group, ethoxy group, isopropoxy group, butoxy group, phenoxy group; polyoxyalkylene group, mercapto group and aryl group (excluding phenyl group), vinyl group, isopropenyl group, allyl group Alkenyl groups such as acryloyl group, meta Acryloyl group, in which Achille group such as methacryloxypropyl was introduced.

  In the present invention, these silicone oils are added to an aqueous slurry composed of leaf-like silica secondary particles in the form of an aqueous emulsion.

  As the aqueous emulsion of these silicone oils, for example, the following commercially available ones can be appropriately selected and used.

  As so-called straight silicone oil aqueous emulsions, Polon MR, Polon MWS, Polon MK-206 (above methyl hydrogen silicone oil emulsion), Polon MF-7, Polon MF-17, Polon MF-32, KM 722A, KM 740, KM 742, KM 782, KM 785, KM 786 , KM787, KM788, KM797, KM860A, KM862, KM905, KM9705 (above dimethyl silicone oil emulsion), KM871P (methyl phenyl silicone oil emulsion), (manufactured by Shin-Etsu Chemical Co., Ltd.), LE-45, LE-46, LE- 48, LE-460, LE-463, LE-3430, FZ-4110, FZ-4116, FZ-4112, FZ- 129, FZ-4138, FZ-4157, FZ-4158, FZ-4170, FZ-4174, FZ-4185, FZ-4188 (more dimethyl silicone oil emulsion) (more than Nihon Unicar), BY22-007, BY22- 080, BY22-029, BY22-050A, BY22-019, BY22-020, BY22-034, BY22-055, BY22-067 (above dimethyl silicone oil emulsion, manufactured by Toray Dow Corning Silicone), TSM630, TSM631 , TSM6341, TSM6343, YMR7212 (above dimethyl silicone oil emulsion, manufactured by GE Toshiba Silicones).

  Moreover, as an aqueous emulsion of a modified silicone oil, Polon MF-18, Polon MF-24, Sonarsil-10 (above epoxy-modified silicone oil emulsion), Polon MF-14, Polon MF-14D, Polon MF-14EC, Polon MF-29, Polon MF-39 Polon MF-44, Polon MF-52, KM907 (more amino-modified silicone oil emulsion) (more than Shin-Etsu Chemical Co., Ltd.), LE-9300, FZ-315, FZ-4602 (more epoxy-modified silicone oil emulsion), FZ-4632 FZ-4635, FZ-4640, FZ-4645, FZ-4658, FZ-4671, FZ-4678 (above amino-modified silicone oil emulsion), FZ 4633, FZ-4638 (carboxyl-modified silicone oil emulsion), FZ-2105 (polyether-modified silicone oil) (manufactured by Nihon Unicar), SM8704C / SM8904 (amino-modified silicone oil emulsion), HMW2220 (divinyl-modified silicone oil emulsion) (Above Toray Dow Corning Silicone), TEX153 (amino-modified silicone oil emulsion), XS65-B8865 (epoxy-modified silicone oil emulsion), XA69-B5476 (aminopolyether-modified silicone oil emulsion) (above GE Toshiba Silicone) Etc.).

  As an apparatus for treating an aqueous slurry composed of leaf-like silica secondary particles with an aqueous emulsion of silicone oil, it is possible to effectively contact the added silicone oil-based aqueous emulsion with the leaf-like silica secondary particles sufficiently suspended. Although there is no particular limitation as long as it exists, it is desirable to carry out with a tank-type container provided with at least stirring means, and preferably heating means and temperature control means. Preferable examples of the stirring means include a paddle type stirrer, a turbine type stirrer, a propeller type stirrer, and a jet stirrer. The treatment time may vary depending on the type of silicone oil used, the concentration of the silicone oil in the slurry, the treatment temperature, the average particle size of the leaf-like silica secondary particles, the slurry concentration, the ratio of the solid basis of the silicone oil to the silica particles, etc. However, it is usually 10 seconds to 60 minutes, preferably 30 seconds to 30 minutes, and most preferably about 1 to 20 minutes. In addition, process temperature is 10-80 degreeC, Preferably it is 15-60 degreeC, More preferably, it is about 20-40 degreeC. In addition, since gas derived from silicone oil may be generated during the treatment, the reaction vessel is open at the top, or an inert gas is circulated in the vessel at all times to accompany the generated gas. What is removed is preferred.

  From the viewpoint that the amount of the aqueous emulsion of silicone oil, which is a silicon compound, can be carried out on a solid basis with respect to the leaf-like silica secondary particles, for example, without causing the slurry to adhere to the wall surface of the slurry by a spray dryer, Preferably it is 2 mass% or more, More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more, Most preferably, it is 10 mass% or more. In addition, the upper limit is not critically defined, but when added excessively (for example, about 45% by mass), since no further effect is achieved, it is economically wasteful, In addition, excessive silicone oil is not preferable because it acts to inhibit the smooth dispersion of particles and the effect of crushing in the crushing step described below. Therefore, the amount of silicone oil added to silica is usually 40% by mass or less, preferably 35% by mass or less, and more preferably 30% by mass or less.

(Drying of silicone oil treatment slurry)
Thus, the slurry of the leaf-like silica secondary particles treated with the silicon compound emulsion in the slurry state is subjected to the drying treatment step 80, and the water 90 is removed to obtain the leaf-like silica powder aggregate 100.

  As a drying device, the slurry of leaf-like silica secondary particles treated with a silicone compound such as silicone oil generally solidifies and solidifies during heating and drying, unlike the case of a simple aqueous slurry not treated with silicone oil. Therefore, any general dryer can be preferably used.

As a preferable drying apparatus, for example, various dryers such as a box-type dryer, an aeration band dryer, a tunnel dryer, a spray dryer, a fluidized bed dryer, a medium fluidized bed dryer, an aeration rotary dryer, and the like are used. Can do. Among these, spray dryers and fluid dryers are particularly preferable because the obtained leaf-like silica particles can be easily crushed. In the case of spray drying, unlike the case of the conventional aqueous slurry, even if the slurry concentration is about 10 to 50% by mass, the dried silica particles do not aggregate and adhere to the apparatus wall surface. The drying conditions may vary depending on the drying apparatus used. For example, in the case of spray drying, the hot air temperature is 140 to 220 ° C., the slurry supply rate is 5 to 30 L / h, and the spray pressure is about 10 to ²⁰ kg / cm ^2. Is done. The spray nozzle may be any of a rotating disk type, a pressure type, and a two-fluid type.

(Dry crushing treatment)
In the present invention, the dried leaf-like silica secondary particles are obtained as loose powder aggregates 100. This aggregate can be made into a monodispersed leaf-like silica secondary particle powder 120 by carrying out a low-load dry crushing step 110.

  As the low-load crusher, various dry crushers can be used, for example, a ball mill, a vibration ball mill, a conical mill, a tube mill, a rod mill, an attrition mill, a pin type mill, a jet mill, a micron mill, a colloid mill, A micro atomizer, majack mill, micronizer, jet mizer, etc. can be arbitrarily selected.

  The crushing time may vary depending on the type of crushing device, the amount of treatment, the intended crushing particle size, etc., but is usually 0.5 to 25 hours, preferably 1 to 20 hours, more preferably 2 to 10 hours. Degree.

  As described above, the pulverized dry particle powder is a highly monodispersed dry silica powder as shown in, for example, a scanning micrograph (SEM) (see FIGS. 2 to 3) in Examples described later. That is confirmed.

  The dry silica powder has an average particle size of, for example, 0.1 to 4.0 μm, preferably 0.2 to 2 by a laser diffraction / scattering type particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.). About 0.0 μm, which is a dry powder of secondary particles of leaf-like silica monodispersed with the same particle size as that in the original water-based slurry state and retaining the particle shape in the slurry state It is. In the present invention, “highly monodispersed” means that dry powder silica is in such a state. The dry silica powder is preferably silica made of layered polysilicic acid, and the main peak in X-ray diffraction analysis is silica corresponding to silica-X and / or silica-Y.

  In the dry silica powder of the present invention, the surface is treated with a silicon compound such as silicone oil. The silica particles are washed with a solvent to extract the silicone oil on the silica surface, and the extract is liquid. It can be easily confirmed by separation and identification by chromatography or the like.

[Example 1]
(Preparation of aqueous slurry composed of secondary silica particles)
Silica hydrogel, which is a starting material for hydrothermal treatment, was prepared as follows using sodium silicate as an alkali source according to a known method. That is, a sodium silicate aqueous solution 2000 mL / min having a SiO ₂ / Na ₂ O = 3.0 (molar ratio), SiO ₂ concentration of 21.0% by mass and a sulfuric acid aqueous solution having a sulfuric acid concentration of 20.0% by mass were released. Introduced into a container equipped with an outlet from a separate inlet, and uniformly mixed instantaneously, adjusted so that the pH of the liquid discharged from the outlet into the air was 7.5 to 8.0, and generated The silica sol solution was continuously discharged from the discharge port into the air and gelled in the air. An aging tank filled with water was placed at the dropping point, dropped and aged here, and sufficiently washed with water to obtain a silica hydrogel having an average particle diameter of 6 mm.

The silica hydrogel particles are coarsely pulverized to an average particle size of 2.5 mm using a double roll crusher, and the total SiO ₂ / Na ₂ in the system is placed in an autoclave (electrically heated, with anchor type stirring blades) of 50000 mL. as O molar ratio is 12.0, 23.7 kg and aqueous sodium silicate solution (SiO ₂ 28.75 wt%, Na ₂ O9.3 _{wt%, SiO 2 / Na 2 O} = 3.17 ( molar ratio )) 5.5 kg was charged, 10.7 kg of ion exchange water was added thereto, and hydrothermal treatment was performed at 185 ° C. for 8 hours while stirring at 50 rpm. The total silica concentration in the system was 15% by mass as SiO ₂ .

  The slurry after the hydrothermal treatment was washed with filtered water using a filter cloth type vertical centrifuge (manufactured by Toko Machine Co., Ltd., TU-18 type), and the solid water content was 69.7% by mass (solid content concentration: 30.3). (Mass%) of a wet cake of silica tertiary aggregate particles.

  To 1000 g of the wet cake (solid content concentration: 30.3% by mass), 1020 g of ion exchange water is added and repulped to prepare 202 g of an aqueous slurry of silica tertiary aggregate particles (solid content of 15% by mass, pH 7.2). did. In this slurry state, the average particle diameter measured by a Coulter counter was 7.2 μm, and the viscosity measured by a B-type viscometer was 0.010 Pa · s.

  The aqueous slurry was mixed with a medium agitation bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL-PILOT A type (Bessel capacity 1.4 L, diameter 0.5 mm zirconia beads 70% filled)) at a shaft rotation speed of 3400 rpm and a flow rate of 10 L / h. The mixture was crushed and dispersed to obtain an aqueous slurry (hereinafter referred to as “aqueous slurry 1”) composed of leaf-like silica secondary particles.

(Treatment of aqueous slurry with silicon compound)
To 2000 g (solid content concentration 15 mass%, average particle size 0.55 μm) of the aqueous slurry 1 of the leaf-like silica secondary particles, a silicon compound (methyl hydrogen silicone oil emulsion, Shin-Etsu Chemical Co., Ltd.) for silica particle surface treatment Product name: Polon MR, solid content concentration 60.0% by mass), 125g is added so that the blending amount is 20% (solid content / total solid content (mass basis, the same applies hereinafter)), and further 1625g of water is added. Then, after diluting to a slurry concentration (total solid content concentration) of 10.0% by mass, the mixture was thoroughly mixed using a stirrer, and the silica was treated for 5 minutes at room temperature in a water / silicon compound mixed slurry state. .

(Drying and crushing process)
Using the spray dryer (GA32 type manufactured by Sakamoto Giken Co., Ltd.), the mixed slurry treated in a slurry state with the silicon-based compound as described above is supplied with a slurry supply rate of 10 L / h, a spray pressure of 15 kg / cm ² , and a hot air temperature of 180. Spray drying was performed at 0 ° C. to obtain a substantially spherical agglomerate of dry powder of leaf-like silica secondary particles surface-treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 11.6 μm.

  250 g of agglomerates of dry powder such as the secondary particles of leafy silica (hereinafter sometimes referred to as “leafy silica powder agglomerates”) are used in a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type). Pot capacity: 1 L Grinding medium: φ5 mm alumina balls 80% filled) was used for crushing treatment for 5 hours to crush the foliar silica powder aggregate.

  The average particle size of the dried particle powder that has been pulverized and monodispersed by a laser diffraction / scattering particle size distribution analyzer (Horiba, LA-920 type) is 0.60 μm, almost in the original slurry state. It was a dry powder of secondary silica particles that had the same particle size and were monodispersed while maintaining the shape of the particles in a slurry state.

  The scanning micrograph (SEM) of the leaf-like silica secondary particles is shown in FIG. 2, and as is clear from this, it was confirmed to be highly monodispersed dry silica powder.

(Silica dry particle powder paint)
In a 300 mL beaker, 5 g of the monodispersed dry particle powder of the leaf-like silica secondary particles obtained in this manner was used as an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A liquid, resin solid content 53%). It mix | blended with 14.9g and stirred and made it uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B liquid, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and stirred. Homogenized to obtain a coating composition. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the leaf-like silica secondary particles (some of which contain primary particles) in the resin are subjected to a drying process that tends to aggregate once. It was confirmed that the particles were not substantially aggregated, were well dispersed in the coating film, and were oriented and laminated in parallel. This is because silica tertiary agglomerate particles are crushed with an aqueous slurry to obtain an aqueous slurry of leaf-like silica secondary particles, which are blended into an aqueous organic paint without drying and remaining as an aqueous slurry with good dispersibility. It is shown that dry silica particles in a state of very good dispersibility, which is almost inferior to those obtained, are obtained. The above results are summarized in Tables 1 and 2. In Table 1, “EM” indicates an emulsion.

[Example 2]
(Preparation of aqueous slurry composed of secondary silica particles)
Silica hydrogel particles having an average particle size of 6 mm obtained in the same manner as in Example 1 were coarsely pulverized to an average particle size of 2.5 mm using a double roll crusher, and a capacity of 5000 mL autoclave (electrically heated, anchor type stirring blade) 2688 g and sodium hydroxide aqueous solution (NaOH 48.5% by mass) 126 g so that the total SiO ₂ / Na ₂ O molar ratio in the system becomes 11.0, and 1186 g of ion-exchanged water is added thereto. In addition, 0.5 g of seed crystals were added, and hydrothermal treatment was performed at 180 ° C. for 12 hours while stirring at 20 rpm. The total silica concentration in the system was 12.5% by mass as SiO ₂ .

  The slurry after the hydrothermal treatment was washed with filtered water using a filter cloth vertical centrifuge (manufactured by Toko Machine Co., Ltd., TU-18 type), and the solid water content was 66.7% by mass (solid content concentration: 33.3). (Mass%) of a wet cake of silica tertiary aggregate particles.

  1220 g of ion-exchanged water is added to 1000 g of the wet cake (solid content concentration: 33.3 mass%) and repulped to prepare 2220 g of an aqueous slurry of silica tertiary aggregate particles (solid content of 15 mass%, pH 7.1). did. In this slurry state, the average particle diameter measured by a Coulter counter was 7.2 μm, and the viscosity measured by a B-type viscometer was 0.010 Pa · s.

  The aqueous slurry was mixed with a medium stirring bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL-PILOT A type (Bessel capacity: 1.4 L, diameter: 0.5 mm, filled with zirconia beads of 70%)) at a shaft rotation speed of 3400 rpm and a flow rate of 10 L / h. The slurry was passed through, crushed and dispersed to obtain an aqueous slurry (hereinafter referred to as “aqueous slurry 2”) composed of secondary silica particles.

(Treatment of aqueous slurry with silicon compound)
To 2000 g (solid content concentration 15 mass%, average particle size 0.56 μm) of the aqueous slurry 2 of leaf-like silica secondary particles, a silicon compound (methyl hydrogen silicone oil emulsion, Shin-Etsu Chemical Co., Ltd.) for silica particle surface treatment Product name: Polon MR, solid content concentration of 60.0% by mass) is added in an amount of 125 g so that the blending amount is 20% (solid content / total solid content), and further, 1625 g of water is added to obtain a total solid content concentration of 10 After dilution to 0.0 mass%, the mixture was thoroughly mixed using a stirrer, and the silica was treated at room temperature for 10 minutes in a water / silicone compound mixed slurry.

(Drying and crushing treatment)
Using the spray dryer (GA32 type manufactured by Sakamoto Giken Co., Ltd.), the mixed slurry treated in a slurry state with the silicon-based compound as described above is supplied with a slurry supply rate of 10 L / h, a spray pressure of 15 kg / cm ² , and a hot air temperature of 180. Spray drying was performed at 0 ° C. to obtain a substantially spherical agglomerate of dry powder of leaf-like silica secondary particles surface-treated with a silicon compound. The average particle diameter of this aggregate by means of a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 12.9 μm.

  250 g of agglomerates (leafy silica powder agglomerates) of the dry powder of the foliar silica secondary particles were added to a small vibration ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L grinding medium: φ5 mm alumina Ball 80% filling) was used for 5 hours to perform pulverization, and the pulverized silica powder aggregate was pulverized.

  The average particle size of the dried particle powder that has been pulverized and monodispersed by a laser diffraction / scattering particle size distribution measuring apparatus (Horiba, LA-920 type) is 0.66 μm, which is almost in the original slurry state. It was a dry powder of secondary particles of leaf-like silica that had an equivalent particle size and was monodispersed while maintaining the shape of the particles in a slurry state.

  A scanning micrograph (SEM) of the leaf-like silica secondary particles is shown in FIG. 3, and as is clear from this, it was confirmed to be a highly monodispersed dry silica powder.

(Silica dry particle powder paint)
In a 300 mL beaker, 5 g of the monodispersed dry particle powder of the leaf-like silica secondary particles obtained in this manner was used as an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A liquid, resin solid content 53%). It mix | blended with 14.9g and stirred and made it uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the secondary silica particles (in which some primary particles are included) are oriented and laminated in parallel without aggregation in the resin. The same situation as when the scaly silica slurry was blended with the aqueous organic paint was observed.

  That is, the silica tertiary aggregate particles were crushed with an aqueous slurry to obtain an aqueous slurry of leaf-like silica secondary particles, and this was blended into an aqueous organic paint without drying, as an aqueous slurry with good dispersibility. As the case shows, dry silica particle powder with very good dispersibility is obtained. The above results are summarized in Tables 1 and 2.

Example 3
(Preparation of aqueous slurry composed of secondary silica particles)
Silica hydrogel particles having an average particle diameter of 6 mm obtained in the same manner as in Example 1 were coarsely pulverized to an average particle diameter of 2.5 mm using a double roll crusher, and an autoclave having a capacity of 50000 mL (electric heating type, anchor type stirring). 23.7 kg and sodium silicate aqueous solution 5.5 kg are charged so that the total SiO ₂ / Na ₂ O molar ratio in the system becomes 12.0, and 10.7 kg of ion-exchanged water is added thereto. In addition, hydrothermal treatment was performed at 185 ° C. for 8 hours while stirring at 50 rpm. The total silica concentration in the system was 15% by mass as SiO ₂ .

  The slurry after the hydrothermal treatment was washed with filtered water using a filter cloth type vertical centrifuge (manufactured by Toko Machine Co., Ltd., TU-18 type), and the solid water content was 69.7% by mass (solid content concentration: 30.3). (Mass%) of a wet cake of silica tertiary aggregate particles.

  Ion exchanged water 1020 g was added to 1000 g of the wet cake (solid content concentration 30.3 mass%) and repulped to prepare 202 g of an aqueous slurry of silica tertiary aggregate particles (solid content 15 mass%, pH 7.2). . In this slurry state, the average particle diameter measured by a Coulter counter was 7.2 μm, and the viscosity measured by a B-type viscometer was 0.010 Pa · s.

  The aqueous slurry was mixed with a medium agitation bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL-PILOT A type (Bessel capacity 1.4 L, diameter 0.5 mm zirconia beads 70% filled)) at a shaft rotation speed of 3400 rpm and a flow rate of 10 L / h. The mixture was crushed and dispersed to obtain an aqueous slurry (hereinafter referred to as “aqueous slurry 3”) composed of leaf-like silica secondary particles.

(Treatment of aqueous slurry with silicon compound)
2000 g (solid content concentration 16% by mass, average particle size 1.41 μm) of the aqueous slurry 3 of the foliar silica secondary particles was added to a silicon compound for surface treatment (methyl hydrogen silicone oil emulsion (manufactured by Shin-Etsu Chemical Co., Ltd.) : Polon MR, solid content concentration of 60.0% by mass) is added in an amount of 133 g so that the blending amount is 20% (solid content / total solid content), and further 1865 g of water is added to obtain a total solid content concentration of 10.0. After dilution to mass%, the mixture was mixed well using a stirrer, and the silica was treated for 5 minutes at room temperature in a water / silicone compound mixed slurry state.

(Drying and crushing process)
Using the spray dryer (GA32 type manufactured by Sakamoto Giken Co., Ltd.), the mixed slurry treated in a slurry state with the silicon-based compound as described above is supplied with a slurry supply rate of 10 L / h, a spray pressure of 15 kg / cm ² , and a hot air temperature of 180. Spray drying was performed at 0 ° C. to obtain a substantially spherical agglomerate of dry powder of leaf-like silica secondary particles surface-treated with a silicon compound. The average particle diameter of this aggregate by means of a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 14.6 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L grinding medium: 80% φ5 mm alumina balls) The pulverization process was performed for 1 hour, and the pulverized silica powder aggregate was pulverized.

  The average particle diameter of the dry powder that has been pulverized and monodispersed using a laser diffraction / scattering particle size distribution analyzer (Horiba Seisakusho, LA-920 type) is 1.33 μm, almost equivalent to that in the original slurry state. It was a dry powder of secondary particles of leaf-like silica monodispersed while maintaining the shape of the particles in a slurry state.

(Silica dry particle powder paint)
14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker is obtained by 5 g of the thus obtained leaf-like silica secondary particle monodispersed dry powder. And stirred to make it uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the leaf-like silica secondary particles (partially primary particles) in the resin are not substantially aggregated even though the drying process is easy to aggregate. It was confirmed that they were well dispersed in the film and were oriented and laminated in parallel.

  As described above, according to the present invention, the silica tertiary aggregate particles are crushed with the aqueous slurry to obtain the aqueous slurry of the leaf-like silica secondary particles, and the aqueous slurry with good dispersibility is obtained without drying. Thus, it is shown that a dry silica particle powder having extremely good dispersibility is obtained as in the case of blending with an aqueous organic paint. The above results are summarized in Tables 1 and 2.

Example 4
(Preparation of aqueous slurry composed of secondary silica particles)
Silica hydrogel particles having an average particle diameter of 6 mm obtained in the same manner as in Example 1 were coarsely pulverized to an average particle diameter of 2.5 mm using a double roll crusher, and an autoclave having a capacity of 50000 mL (electric heating type, anchor type stirring). 23.7 kg and sodium silicate aqueous solution 5.5 kg are charged so that the total SiO ₂ / Na ₂ O molar ratio in the system becomes 12.0, and 10.7 kg of ion-exchanged water is added thereto. In addition, hydrothermal treatment was performed at 185 ° C. for 8 hours while stirring at 50 rpm. The total silica concentration in the system was 15% by mass as SiO ₂ .

  The slurry after the hydrothermal treatment was washed with filtered water using a filter cloth type vertical centrifuge (manufactured by Toko Machine Co., Ltd., TU-18 type), and the solid water content was 69.7% by mass (solid content concentration: 30.3). (Mass%) of a wet cake of silica tertiary aggregate particles.

  894 g of ion-exchanged water was added to 1000 g of the wet cake (solid content concentration of 30.3 mass%) and repulped to prepare 1894 g of an aqueous slurry of silica tertiary aggregate particles (solid content of 16 mass%, pH 7.2). . In this slurry state, the average particle diameter measured by a Coulter counter was 7.2 μm, and the viscosity measured by a B-type viscometer was 0.012 Pa · s.

  The aqueous slurry was mixed with a medium agitation bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL-PILOT A type (filled with a vessel capacity of 1.4 L and a diameter of 0.5 mm zirconia beads of 70%)) at a shaft rotation speed of 3400 rpm and a flow rate of 30 L / h. The mixture was crushed and dispersed to obtain an aqueous slurry (hereinafter referred to as “aqueous slurry 4”) composed of leaf-like silica secondary particles.

(Treatment of aqueous slurry with silicon compound)
To 2000 g (solid content concentration 16% by mass, average particle size 1.44 μm) of the aqueous slurry 4 of the leaf-like silica secondary particles, a silicon compound for surface treatment (methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd.) Polon MR, solid content concentration of 60.0 mass%) is added to 133g so that the blending amount is 20% (solid content / total solid content), and further 1865g of water is added to dilute to a total solid content concentration of 10.0 mass% Thereafter, the mixture was thoroughly mixed using a stirrer, and the silica was treated for 10 minutes at room temperature in a water / silicone compound mixed slurry state.

(Drying and crushing process)
Using the spray dryer (GA32 type manufactured by Sakamoto Giken Co., Ltd.), the mixed slurry treated in the slurry state with the silicon compound as described above is supplied with a slurry supply rate of 10 L / h, a spraying pressure of 15 kg / cm ² , and a hot air temperature of 180. Spray drying was performed at 0 ° C. to obtain a substantially spherical agglomerate of dry powder of leaf-like silica secondary particles surface-treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 14.0 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L grinding medium: 80% φ5 mm alumina balls) The pulverization process was performed by operating for 1 hour, and the pulverized silica powder aggregate was pulverized.

  The average particle diameter of dry powder that has been pulverized and monodispersed by a laser diffraction / scattering particle size distribution analyzer (Horiba, LA-920 type) is 1.29 μm, which is almost the same as in the original slurry state. It was a dry powder of secondary particles of leaf-like silica monodispersed while maintaining the shape of the particles in a slurry state.

(Silica dry particle powder paint)
14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker is obtained by 5 g of the thus obtained leaf-like silica secondary particle monodispersed dry powder. And mixed to make uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the leaf-like silica secondary particles (partially primary particles) in the resin are not substantially aggregated even though the drying process is easy to aggregate. It was confirmed that they were well dispersed in the film and were oriented and laminated in parallel.

That is, according to the leaf-like silica secondary particle monodispersed dry powder of the present invention, the silica tertiary aggregate particles are crushed with an aqueous slurry to obtain an aqueous slurry of the leaf-like silica secondary particles, which are dispersed without drying. It shows that a dry silica particle powder having a very good dispersibility, which is inferior to that when blended in an aqueous organic paint, with a water-based slurry having good properties, is obtained.
The above results are summarized in Table 1 and Table 2.

Example 5
A similar experiment was conducted except that the compounding amount of the silicon compound in Example 1 was changed to 10%. The results are shown in Tables 1 and 2.

Example 6
A similar experiment was conducted except that the blending amount of the silicon compound in Example 1 was changed to 30%. The results are shown in Tables 1 and 2.

Example 7
A similar experiment was conducted except that the compounding amount of the silicon compound in Example 3 was changed to 10%. The results are shown in Tables 1 and 2.

Example 8
A similar experiment was conducted except that the blending amount of the silicon compound in Example 3 was changed to 30%. The results are shown in Tables 1 and 2.

Example 9
A similar experiment was conducted except that in Example 1, a dimethyl silicone oil emulsion (trade name: KM905, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicon-based compound for silica surface treatment. The results are shown in Tables 1 and 2.

Example 10
The same experiment as in Example 1 was performed except that dimethyl silicone oil emulsion (trade name: FZ-4158, manufactured by Nihon Unicar Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 1. The results are shown in Tables 1 and 2.

Example 11
The same experiment as in Example 1 was performed except that an amino-modified dimethyl silicone oil emulsion (trade name: KM907, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 1. The results are shown in Tables 1 and 2.

Example 12
The same experiment as in Example 1 was carried out except that an epoxy-modified dimethyl silicone oil emulsion (trade name: Sofnersil-10, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 1. The results are shown in Tables 1 and 2.

Example 13
Example 1 except that a carboxyl-modified dimethyl silicone oil emulsion (trade name: FZ-4633, manufactured by Nihon Unicar Co., Ltd.) was used as the silicon-based compound for silica surface treatment in Example 1, and the crushing time was 10 hours. A similar experiment was conducted. The results are shown in Tables 1 and 2.

Example 14
Example 1 except that a polyether-modified dimethyl silicone oil emulsion (trade name: FZ-2105, manufactured by Nihon Unicar Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 1, and the crushing time was 10 hours. The same experiment was conducted. The results are shown in Tables 1 and 2. Although FZ-2105 is “Oil”, it itself has a polyether group, so when it is added to the aqueous slurry, it is well dispersed in an aqueous solvent to form an emulsion.

Example 15
The same experiment as in Example 3 was performed except that dimethyl silicone oil emulsion (trade name: FZ-4158, manufactured by Nihon Unicar) was used as a silicon-based compound for silica surface treatment in Example 3. The results are shown in Tables 1 and 2.

Example 16
The same experiment as in Example 3 was performed except that an amino-modified dimethyl silicone oil emulsion (trade name: KM907, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 3. The results are shown in Tables 1 and 2.

Example 17
The same experiment as in Example 3 was carried out except that an epoxy-modified dimethyl silicone oil emulsion (trade name: Sofnersil-10, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicon compound for silica surface treatment in Example 3. The results are shown in Tables 1 and 2.

Example 18
In Example 3, a carboxyl-modified dimethyl silicone oil emulsion (trade name: FZ-4633, manufactured by Nihon Unicar Co., Ltd.) was used as the silicon compound for silica surface treatment, and the crushing time was 3 hours. The experiment was conducted. The results are shown in Tables 1 and 2.

Example 19
In Example 3, a polyether-modified dimethyl silicone oil emulsion (trade name: FZ-2105, manufactured by Nihon Unicar Co., Ltd.) was used as the silicon-based compound for silica surface treatment, and the crushing time was 3 hours. A similar experiment was conducted. The results are shown in Tables 1 and 2. Although FZ-2105 is “Oil”, it itself has a polyether group, so when it is added to the aqueous slurry, it is well dispersed in an aqueous solvent to form an emulsion.

[Comparative Example 1]
(Treatment of water-based slurry without addition of silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15 mass%, average particle size 0.55 μm) of aqueous slurry 1 of leaf-like silica secondary particles after wet pulverization prepared in the same manner as Example 1. In addition, 1000 g of water was further added and diluted to a total solid content concentration of 10.0% by mass, and then mixed well for 5 minutes using a stirrer.

(Drying and crushing process)
The mixed slurry is further diluted 10 times by adding water, and using a spray dryer (model number: 2ND-140-10S manufactured by Sakamoto Giken Co., Ltd.), the diluted slurry supply amount is 10 L / h, and the spraying pressure is 15 kg / cm ^2. Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical agglomerate of dried powder of leaf-like silica secondary particles. The average particle diameter of this aggregate by a laser diffraction / scattering particle size distribution analyzer (LA-920 type, manufactured by Horiba, Ltd.) was 12.1 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: φ5 mm alumina balls 80% packed) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  The average particle diameter of the pulverized dry powder measured by a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., LA-920 type) is 8.10 μm, and the average particle diameter in the original slurry state (average Compared with a particle diameter of 0.55 μm, the particle diameter was significantly larger. Moreover, when the shape was visually observed, it was recognized that the dry powder aggregate state remained. A scanning micrograph (SEM) of the dry powder is shown in FIG. 4, and as is clear from this, it was confirmed that the silica dry powder was in an aggregated state.

(Silica dry particle powder paint)
In a 300 mL beaker, 5 g of the obtained dried leafy silica secondary particle powder was blended with 14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 clear A solution, resin solid content 53%). Stir to homogenize. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a cloudy film with no transparency. The results are shown in Tables 1 and 2.

[Comparative Example 2]
(Treatment of water-based slurry without addition of silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15% by mass, average particle size 1.41 μm) of aqueous slurry 3 of leaf-like silica secondary particles after wet crushing prepared in the same manner as Example 3. The mixture was further mixed with 1000 g of water and diluted to a total solid content concentration of 10.0% by mass, followed by stirring for 5 minutes using a stirrer.

(Drying and crushing process)
The mixed slurry is further diluted 10 times by adding water, and using a spray dryer (model number: 2ND-140-10S manufactured by Sakamoto Giken Co., Ltd.), the diluted slurry supply amount is 10 L / h, and the spraying pressure is 15 kg / cm ^2. Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical agglomerate of dried powder of leaf-like silica secondary particles. The average particle diameter of this aggregate by a laser diffraction / scattering particle size distribution analyzer (LA-920 type, manufactured by Horiba, Ltd.) was 12.1 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: φ5 mm alumina balls 80% packed) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  The average particle diameter of the pulverized dry powder measured by a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., LA-920 type) is 5.52 μm, and the average particle diameter in the original slurry state (average Compared with a particle size of 1.41 μm), the particle size was significantly larger. Moreover, when the shape was observed visually, it was recognized that the state of the dry powder aggregate remained. A scanning micrograph (SEM) of the dry powder is shown in FIG. 5, and as is clear from this, it was confirmed that the silica dry powder was in an aggregated state.

(Silica dry particle powder paint)
In a 300 mL beaker, 5 g of the obtained dried leafy silica secondary particle powder was blended with 14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 clear A solution, resin solid content 53%). Stir to homogenize. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a cloudy film with no transparency. The results are shown in Tables 1 and 2.

[Comparative Example 3]
(Treatment by adding excess silicon compound in water slurry)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15 mass%, average particle size 0.55 μm) of aqueous slurry 1 of leaf-like silica secondary particles after wet pulverization prepared in the same manner as Example 1. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) is added so that the blending amount is 45% (solid content / total solid content), and water is added. Was added and diluted to a total solid content concentration of 10.0% by mass, followed by thorough mixing using a stirrer, and the silica was treated for 10 minutes at room temperature in a water / silicone compound mixed slurry state.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by means of a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 12.4 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: φ5 mm alumina balls 80% packed) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  However, it was observed that most of the powder aggregate after the pulverization treatment was aggregated and adhered to the entire wall surface under the pot of the vibration ball mill. When this aggregate was forcibly scraped off and the particle size was measured with a laser diffraction / scattering type particle size distribution analyzer (manufactured by Horiba, Ltd., LA-920 type), the average particle size was 9.05 μm. Compared with the particle size in the slurry state (average particle size 0.55 μm), the particle size was significantly larger. Further, when the shape was observed with the naked eye, it was recognized that the state of the dry powder agglomerate remained largely and was not sufficiently monodispersed.

  From this, when the compounding amount of the silicon compound is about 45% by mass, it can be dried by a spray dryer, but an excess oily silicon compound is present in the particle aggregate, so that vibration is caused. Even when vibration is applied in the ball mill, it is presumed that the excessive oily compound acts to bind the particles rather, thereby inhibiting the crushing effect.

(Silica dry particle powder paint)
14.9 g of organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker of 5 g of dry powder of secondary silica particles obtained by scraping was obtained. And stirred to make it uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a cloudy film with no transparency. The results are shown in Tables 1 and 2.

[Comparative Example 4]
(Treatment by adding excess silicon compound in water slurry)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15% by mass, average particle size 1.41 μm) of aqueous slurry 3 of leaf-like silica secondary particles after wet crushing prepared in the same manner as Example 3. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) is added so that the blending amount is 45% (solid content / total solid content), and water is added. Was added and diluted to a total solid content concentration of 10.0% by mass, followed by thorough mixing using a stirrer, and the silica was treated for 10 minutes at room temperature in a water / silicone compound mixed slurry state.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 12.8 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: filled with 80% φ5 mm alumina balls) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  However, it was observed that most of the powder aggregate after the pulverization treatment was aggregated and adhered to the entire wall surface under the pot of the vibration ball mill. The aggregate was forcibly scraped off and the particle size was measured with a laser diffraction / scattering type particle size distribution analyzer (Horiba, LA-920 type). The average particle size was 5.19 μm, Compared with the particle size in the slurry state (average particle size of 1.41 μm), the particle size was significantly larger. Further, when the shape was observed with the naked eye, it was recognized that the state of the dry powder agglomerate remained largely and was not sufficiently monodispersed.

  That is, when the compounding amount of the silicon compound is about 45% by mass, drying with a spray dryer can be performed, but an excess oily silicon compound exists in the particle aggregate. It is presumed that, even when vibration is applied, the excess oily compound acts to bind the particles to each other and inhibits the effect of crushing.

(Silica dry particle powder paint)
14.9 g of organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker of 5 g of dry powder of secondary silica particles obtained by scraping was obtained. And stirred to make it uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a cloudy film with no transparency. The results are shown in Tables 1 and 2.

Example 20
(Treatment of aqueous slurry with silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15 mass%, average particle size 0.55 μm) of aqueous slurry 1 of leaf-like silica secondary particles after wet pulverization prepared in the same manner as Example 1. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) was added in an amount of 26 g so that the blending amount was 5% (solid content / total solid content). After adding 1130 g of water and diluting to a total solid concentration of 10.0% by mass, the mixture was thoroughly mixed using a stirrer, and the silica was treated in a water / silicone compound mixed slurry state at room temperature for 5 minutes.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 13.3 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: filled with 80% φ5 mm alumina balls) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  The average particle size of the pulverized dry powder measured by a laser diffraction / scattering type particle size distribution analyzer (manufactured by Hori Seisakusho, LA-920 type) is 0.67 μm, and the average particle size in the original slurry state (average The particle diameter was approximately the same as the particle diameter of 0.55 μm), and was a dry powder of secondary dispersed leaf-like silica particles that retained the shape of the particles in a roughly slurry state.

(Silica dry particle powder paint)
14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker is obtained by 5 g of the thus obtained leaf-like silica secondary particle monodispersed dry powder. And mixed to make uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the leaf-like silica secondary particles (partially primary particles) in the resin are not substantially aggregated even though the drying process is easy to aggregate. It was confirmed that they were well dispersed in the film and were oriented and laminated in parallel. The results are shown in Tables 1 and 2.

Example 21
(Treatment of aqueous slurry with silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15% by mass, average particle size 1.41 μm) of aqueous slurry 3 of leaf-like silica secondary particles after wet crushing prepared in the same manner as Example 3. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) is added 28 g so that the blending amount is 5% (solid content / total solid content). After adding 1340 g of water and diluting to a total solid concentration of 10.0% by mass, the mixture was thoroughly mixed using a stirrer, and the silica was treated in a water / silicone compound mixed slurry state at room temperature for 5 minutes.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering type particle size distribution analyzer (LA-920 type, manufactured by Horiba, Ltd.) was 15.0 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: filled with 80% φ5 mm alumina balls) The pulverization process was performed by operating for 3 hours, and the pulverized silica powder aggregate was pulverized.

  The average particle diameter of the dried powder subjected to the pulverization treatment by a laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.) is 1.34 μm, and the particle diameter in the slurry state (average particle diameter) It was a dry powder of secondary particles of leaf-like silica monodispersed while maintaining the shape of particles in a slurry state.

(Silica dry particle powder paint)
14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 Clear A solution, resin solid content 53%) in a 300 mL beaker is obtained by 5 g of the thus obtained leaf-like silica secondary particle monodispersed dry powder. And mixed to make uniform. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content.
The appearance of the obtained coating film was a translucent smooth glossy film.

  When the cross-sectional shape of this coating film is observed with a TEM, the leaf-like silica secondary particles (partially primary particles) in the resin are not substantially aggregated even though the drying process is easy to aggregate. It was confirmed that they were well dispersed in the film and were oriented and laminated in parallel. The results are shown in Tables 1 and 2.

[Example 22]
(Treatment of aqueous slurry with silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15 mass%, average particle size 0.55 μm) of aqueous slurry 1 of leaf-like silica secondary particles after wet pulverization prepared in the same manner as Example 1. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) is added with 356 g so that the blending amount is 40% (solid content / total solid content). After adding 2980 g of water and diluting to a total solid concentration of 10.0% by mass, the mixture was thoroughly mixed using a stirrer, and the silica was treated for 10 minutes at room temperature in a water / silicone compound mixed slurry state.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., LA-920 type) was 14.9 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: φ5 mm alumina balls 80% packed) The pulverization process was performed by operating for 10 hours, and the pulverized silica powder aggregate was pulverized.

  Part of the powder aggregate after pulverization was found to adhere to the wall at the bottom of the pot of the vibrating ball mill, but most of the powder was obtained as pulverized and monodispersed dry powder. . The average particle size by the laser diffraction / scattering type particle size distribution analyzer (Horiba, LA-920 type) is 0.68 μm, which is approximately the same particle size as in the original slurry state. It was a dry powder of secondary dispersion of leaf-like silica monodispersed while maintaining the shape.

(Silica dry particle powder paint)
Into a 300 mL beaker, 5 g of the obtained leaf-like silica secondary particle monodispersed dry powder was added to 14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 clear A solution, resin solid content 53%). Blended and stirred to homogenize. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a translucent smooth glossy film. The results are shown in Tables 1 and 2.

Example 23
(Treatment of aqueous slurry with silicon compound)
Silicon compound for silica particle surface treatment was added to 2000 g (solid content concentration 15% by mass, average particle size 1.41 μm) of aqueous slurry 3 of leaf-like silica secondary particles after wet crushing prepared in the same manner as Example 3. (Methyl hydrogen silicone oil emulsion, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Polon MR, solid content concentration 60.0% by mass) is added with 356 g so that the blending amount is 40% (solid content / total solid content). After adding 2980 g of water and diluting to a total solid concentration of 10.0% by mass, the mixture was thoroughly mixed using a stirrer, and the silica was treated at room temperature for 10 minutes in a water / silicone compound mixed slurry state.

(Drying and crushing process)
The mixed slurry treated in a slurry state with the silicon compound in this manner is supplied with a slurry supply amount of 10 L / h and a spray pressure of 15 kg / cm ² using a spray dryer (manufactured by Sakamoto Giken, model number: 2ND-140-10S). Then, spray drying was performed at a hot air temperature of 180 ° C. to obtain a substantially spherical aggregate of dry powder of secondary particles of foliar silica treated with a silicon compound. The average particle diameter of this aggregate by a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was 13.1 μm.

  Using a small vibrating ball mill (manufactured by Chuo Kako Co., Ltd., machine name: MB-1 type, pot content: 1 L, grinding medium: φ5 mm alumina balls 80% packed) The pulverization process was performed by operating for 3 hours, and the pulverized silica powder aggregate was pulverized.

  Part of the powder aggregate after pulverization was found to adhere to the wall at the bottom of the pot of the vibrating ball mill, but most of the powder was obtained as pulverized and monodispersed dry powder. . The average particle size by the laser diffraction / scattering type particle size distribution analyzer (Horiba, LA-920 type) is 1.49 μm, which is almost the same as that in the original slurry state. It was a dry powder of secondary dispersion of leaf-like silica monodispersed while maintaining the shape.

(Silica dry particle powder paint)
Into a 300 mL beaker, 5 g of the obtained leaf-like silica secondary particle monodispersed dry powder was added to 14.9 g of an organic solvent-type urethane resin clear coating (manufactured by Cashew, Stron AS # 65 clear A solution, resin solid content 53%). Blended and stirred to homogenize. Next, 7.5 g of a curing agent for exclusive use of the above-mentioned paint (manufactured by Cashew, Stron AS # 65 Clear B solution, resin solid content 51%) and 3.7 g of thinner (manufactured by Cashew, Stron # 2510) are added and homogenized with stirring. Thus, a coating composition was obtained. The solid content mass ratio of silica and resin in the composition is 30:70.

A glass plate (soda lime glass, 70 mm × 150 mm × 2 mm thickness) is prepared, and the coating composition is applied by a bar coater coating method (JIS K5400) using a # 80 bar coater (manufactured by Eto Kikai Co., Ltd.). And it dried at room temperature for 24 hours to make a test piece. The coating amount was about 20 g / m ² in terms of solid content. The appearance of the obtained coating film was a translucent smooth glossy film. The results are shown in Tables 1 and 2.

  According to the present invention, highly monodispersed silica particle powder composed of silica flake primary particles and / or foliar silica secondary particles can be obtained from the aqueous slurry without using an organic solvent or the like by a simple means. It can be easily obtained by drying while maintaining the state in the water slurry. The dry particle powder of the secondary silica particles is extremely useful as a filler for remarkably improving the film quality and the like in various coating forming compositions such as paints, coating agents, floor polish compositions, adhesives and cosmetics. It is useful.

It is a flow sheet of the manufacturing method of the monodispersed dry silica particle powder of this invention. It is a SEM photograph of dry silica particle powder. It is a SEM photograph of dry silica particle powder. It is a SEM photograph of dry silica particle powder. It is a SEM photograph of dry silica particle powder.

Explanation of symbols

10 Silica hydrogel, etc. 20 Hydrothermal reaction process
30 Silica tertiary aggregate particle water slurry 40 Crushing / dispersing treatment step in slurry 50 Leaf-like silica secondary particle aqueous slurry 60 Silicon compound aqueous emulsion 70 Treatment step in silica aqueous slurry 80 Slurry drying treatment step 90 Water 100 Foliated silica powder aggregate 110 Dry crushing treatment step 120 Monodispersed dry silica particle powder

Claims (8)

  Highly monodispersed dry silica particles characterized in that they are composed of silica flake primary particles and / or leaf-like silica secondary particles formed by overlapping a plurality of the primary particles in parallel with each other. Powder.   The dry silica particle powder according to claim 1, wherein the surface is treated with a silicon compound.   The dry silica particle powder according to claim 1 or 2, wherein the silica flake primary particles and / or the leaf-like silica secondary particles are layered polysilicic acid.   The main peak in the X-ray diffraction analysis of the silica flake primary particles and / or the leaf-like silica secondary particles is silica corresponding to silica-X and / or silica-Y. The dry silica particle powder described.   A method for producing a dry silica particle powder in which silica flake primary particles and / or leaf-like silica secondary particles are highly monodispersed, wherein (i) silica hydrogel, activated silicic acid or hydrous silicic acid is alkali Hydrothermal treatment is performed in the presence of a metal salt, and the flaky primary particles of scaly silica are oriented in parallel with each other in parallel with each other, and the flaky silica secondary particles are three-dimensional. (Ii) pulverizing and dispersing the silica tertiary aggregate particles in an aqueous slurry state, and A step of forming an aqueous slurry comprising silica flake primary particles and / or leaf-like silica secondary particles; (iii) an aqueous slurry comprising said silica flake primary particles and / or leaf-like silica secondary particles; A process comprising adding and mixing a compound water-based emulsion to treat in a slurry state, (iv) a drying process for drying the mixture, and (v) dry crushing the dry powder. A method for producing monodispersed dry silica particle powder.   The method for producing a dry silica particle powder according to claim 5, wherein the silicon-based compound aqueous emulsion is added to and mixed with 2% by mass or more of the silicon-based compound aqueous emulsion on a solid basis.   The method for producing a dry silica particle powder according to claim 5 or 6, wherein the silica flake primary particles and / or the leaf-like silica secondary particles are layered polysilicic acid.   The main peak in the X-ray diffraction analysis of the thin flake primary particles and / or the leaf-like silica secondary particles is silica corresponding to silica-X and / or silica-Y. The manufacturing method of the dry silica particle powder of description.

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